This invention relates to disposable containers having covers and particularly to such a container wherein the cover is releasably interlocked with the container by a bayonet closure, or similar closure means requiring rotational movement of the cover relative to the container.
In the use of covered containers to package, distribute and display food items it is desirable that the cover be of a transparent material to permit visual inspection of the packaged food. Therefore, and since the economies of disposable or non-reusable packaging demands a lightweight material for the cover, the cover normally is a see-through plastic of delicate and fragile construction. Such lightweight material does not offer the rigidity necessary for the use of standard closure means, such as crimping, and accordingly, securement of the cover to the container has been by heat sealing, sealing tape or stapling, depending on the composition of the container, or by forming the cover to provide a depending flange or portions of a flange to "snap-over" the rim of the underlying container. The sealing type closures are relatively expensive and the "snap" type closures result in loose or otherwise ineffective closures.
An inexpensive, positive closure, such as the bayonet type, that can be effective by interlocking the cover and container through rotational movement of one relative to the other is highly desirable. However, such a closure is difficult to achieve since the fragile nature of the lightweight plastic cover does not lend itself to the physical handling and manipulation for the required rotational movement. Furthermore, the problem is compounded when the cover is formed as a deep dome, such as to accommodate a two or three layer cake, which provides an unwidely configuration.
Accordingly, it is the primary object of this invention to overcome these disadvantages and provide a bayonet closure for locking a cover on a container, wherein the cover is formed of a fragile material.